Recently, the Internet has been widely prevalent, and services such as the Internet telephone, an instant message, and the like, are being widely used. One technology for improving the conveniences of such services is a presence service. In the presence service, a server device called a presence server device collects or receives a status of electric equipment or a status of a user as status information through electric equipment that can be communicated to the server device, and notifies a client device that is a reference person terminal wishing to refer to the status information of the status information.
The presence service is disclosed in, for example, Japanese Patent Unexamined Publication No. 2001-84195 (hereinafter, referred to as patent document 1) and Japanese Patent Unexamined Publication No. 2004-72485 (hereinafter, referred to as patent document 2). In many cases of the presence services, a client device receiving status information previously notifies a presence server device by a message and the like that the client device will receive a part of the information held by the presence server device. Then, the client device allows the presence server device to transmit the status information only when the status information is changed.
There are some methods used as specific protocols for realizing the presence service. In the following description, a method using SIP (Session Initiation Protocol) is briefly described.
FIG. 30 is a sequence diagram showing a conventional information notification system for realizing a presence service. In FIG. 30, server device 100 as an information notification relay device is coupled to user device 105 that manages presence information of a user and the like and information notification terminal 106 of electronic equipment and the like, and manages the statuses of user device 105 and information notification terminal 106. When a status of information notification terminal 106 itself is changed (for example, the power supply is turned on/off) and when a status of a user managed by user device 105 is changed (for example, a user is present or absent), information notification terminal 106 and user device 105 obtain status information indicating the status and transmit the information to server device 100 by setting the information in a PUBLISH message of SIP, respectively (S3001). In FIG. 30, user device 105 transmits information indicating the presence of a user to server device 100. Similarly, information notification terminal 106 may transmit information indicating that the power supply is turned on to server device 100. Hereinafter, user device 105 is described.
Herein, user device 105 obtains a status of a user based on, for example, the user's key operation, or obtains a status of a user by using a sensor without operation.
Server device 100 stores and holds the received status information in a memory and the like, and transmits a response message “200 OK” as a response message to information notification terminal 106 that has transmitted a message (S3002).
On the other hand, when reference person terminal 102 that is a client device wants to know the status information of user device 105, reference person terminal 102 transmits a SUBSCRIBE message specifying the status information of user device 105 to server device 100 (S3003). When server device 100 receives the SUBSCRIBE message, it transmits a response message “200 OK” to reference person terminal 102 (S3004) and transmits a NOTIFY message of SIP setting the previously held status information of user device 105 (user device 105: present) to reference person terminal 102 (S3005). When reference person terminal 102 receives the NOTIFY message setting the status information, it displays the message on a display and transmits a response message “200 OK” to server device 100 (S3006).
Then, when the status of user device 105 is changed, for example, a user managed by user device 105 becomes absent, this information is set in a PUBLISH message of SIP and transmitted to server device 100 (S3007). When server device 100 receives the PUBLISH message, it stores and holds the PUBLISH message in a memory and the like and transmits a response message “200 OK” to user device 105 (S3008).
Thereafter, server device 100 sets the status information of user device 105 (for example, user 105: absent), which was previously stored and held, in a NOTIFY message of SIP and transmits it to reference person terminal 102 (S3009). When reference person terminal 102 receives the NOTIFY message, it displays the received message on a display and transmits a response message “200 OK” to server device 100 (S3010). Thus, a series of operations are terminated.
Similarly, when reference person terminal 103 wants to know the status information of user device 105 or information notification terminal 106, the above-mentioned procedure is executed.
Thus, in a conventional information notification system, when reference person terminal 102 wants to know the status information of information notification terminal 106 and user device 105, or when the status information of information notification terminal 106 and user device 105 is changed, the status information of information notification terminal 106 and user device 105 can be obtained from server device 100, respectively, and can be displayed on a display.
However, in a conventional information notification system, when the number of reference person terminals 102 receiving notification from server device 100 is increased, or the number of information notification terminals 106 and user devices 105 managed by server device 100 is increased, it is thought that the status updating frequency of information notification terminal 106 and user device 105 is increased and the traffic with respect to the notification of the status information is increased. Due to this increase of the traffic, load to server device 100 is extremely increased and may exceed the processing performance of server device 100 depending upon the load level. Consequently, not all of the status information from information notification terminal 106 and user device 105 can be processed. Furthermore, the notification of the status information to reference person terminal 102 may not be carried out satisfactorily.
In particular, in a presence service, remarkably many status changes may occur for a short time, for example, a plurality of users managed by user device 105 attend the same meeting or all users leave for lunch during the lunch break. In such a case, even if server device 100 holds a sufficient processing performance on average, many status notifications from information notification terminal 106 are generated for an extremely short time, which may exceed the processing performance of server device 100. As a result, status notifications may be discarded.
Furthermore, even if status notification is not discarded, the processing of status notification may be extremely delayed. When server device 100 functions as a server device for another service, the quality of the other service may be deteriorated.
Then, in order to dissolve such problems, for example, patent document 2 discloses that when information notification occurs from a plurality of information notification terminals 106, such pieces of information are gathered and transmitted to reference person terminal 102 at a time.
However, since the information notification system described in patent document 2 gathers a plurality of pieces of status information and transmits them to reference person terminal 102 at a time, reference person terminal 102 needs a specific program capable of interpreting the gathered status information. Therefore, such functions must be mounted in all reference person terminals 102.
Furthermore, in the information notification system described in patent document 2, only when a plurality of status notifications are transmitted with respect to the same reference person terminal 102, the number of status notifications to be transmitted by server device 100 can be reduced. When a large number of reference person terminals 102 receive status information transmitted from information notification terminal 106, the effect of reducing the load to server device 100 cannot be obtained. Then, there remains a problem that status notification may be considerably delayed or discarded.
Furthermore, the information notification system described in patent document 2 employs a method of gathering a plurality of pieces of status information and transmitting them to reference person terminal 102 at a time according to the regular updating timing of status information. Thus, the notification to reference person terminal 102 may be delayed until the regular update of status information is carried out.
Furthermore, in the information notification system described in patent document 2, the numbers of information notification terminals, reference person terminals and pieces of information to be referred to are increased, and burst-like traffic of information notifications occurs, thus increasing a load to a server device. To solve this increase in the load to the server device, the following method is thought, that is, hardware specification of server device 100 is improved, or a plurality of server devices 100 are provided and the load is distributed to the plurality of server devices 100. However, in such methods, a configuration of the entire system becomes complicated and the cost of the entire system is increased.